I noticed that if the collars are even in front, one side is higher by about 1/2 inch over the other side. I had to drop the perch on one side so the ride height in front is even.

I've never seen this with any coilover install. Sometimes it is a little off when setting by collar height but 1/2 inch difference between left and right is quite a bit.

Is this normal for the Sleeve-over?

Assuming your off in the front. If that is the case then the perch got hammered into one strut more than the other. Its a friction fit and it can take a lot of pounding to get it fully seated. It's not the end of the world if they are off, just adjust it in the collar to level it out.